Problem: A rectangle is $4$ units long. The rectangle is also $5$ units wide. What is its perimeter?
Explanation: $4\text{ }$ $5\text{ }$ The perimeter is the total length of all the sides of the shape added together. Add up the lengths of the sides: $ \text{perimeter} = {5} + {4} + {5} + {4} $ $ \text{perimeter} = 18\text{ } $